This invention relates to a display apparatus of the projection type wherein an image obtained by irradiating light from a light source upon a light valve is projected on a screen or a like element, and more particularly to a display apparatus of the type which includes a forced air cooling apparatus which includes a cooling fan.
Conventionally, such an apparatus as shown in FIGS. 9 and 10 is known as a liquid crystal projector apparatus which is an example of a display apparatus of the projection type. Referring to FIGS. 9 and 10, the liquid crystal projector apparatus 1 shown includes an outer housing 2 formed in a flattened parallelepiped configuration from a metal sheet or the like. Four stands 3 at which the liquid crystal projector apparatus 1 is placed on a desk or the like are mounted at four corners of the bottom of the outer housing 2. An optical unit case 4 is mounted horizontally at an intermediate position in the vertical direction of the inside of the outer housing 2. The optical unit case 4 is formed in a flattened configuration from a metal sheet or the like and is bent such that it has a substantially L-shape in plane. An optical unit 5 for projecting a color image on a screen or the like is accommodated horizontally in the inside of the optical unit case 4.
The optical unit 5 includes a fly eye lens set 7 serving as illumination optical means and a PS conversion element 8 disposed in series on an optical axis P1 of a discharge lamp 6 serving as a light source. The optical axis P1 is bent by 90xc2x0 into an optical axis P2 by means of a mirror 9, and two dichroic mirrors 10R and 10G for R (red) and G (green) serving as light decomposition means are disposed in series in a spaced relationship from each other and in an inclined relationship by 45xc2x0 on the optical axis P2 bent from the optical axis P1. The dichroic mirrors 10R and 10G and a reflecting mirror 103 provide three optical axes P3, P4 and P5 all bent perpendicularly to the optical axis P2. Three condenser lenses 11R, 11G and 11B and three spatial optical modulation elements 12R, 12B and 12B for R, G and B (blue) such as transmission type liquid crystal panels or the like serving as optical modulation means are disposed on the optical axes P3, P4 and P5, respectively. A cross prism 13 of a square shape serving as optical synthesis means is disposed on an optical axis P6 of the three spatial optical modulation elements 12R, 12G and 12B. Further, a projection lens 14 is disposed on the outgoing side of the cross prism 13 so that image light outgoing from the three spatial optical modulation elements 12R, 12G and 12B for R, G and B such as transmission type liquid crystal display panels serving as optical modulation means is projected on a screen or the like.
The fly eye lens set 7 decomposes light L1 from the discharge lamp 6, which has an intensity distribution, into a large number of light spots. The large number of light spots are superposed on one another by spatial optical modulation elements to make uniform the brightness distribution of the illumination light upon the entire screen of the spatial optical modulation elements 12R, 12G and 12B. The PS conversion element 8 is composed of a plurality of polarizing beam splitters arranged in a rectangular configuration and a plurality of phase difference plates provided intermittently corresponding to the polarizing beam splitters, and converts the polarization direction of the light L1 from the discharge lamp 6 so that, for example, a P wave component of the light L1 may be converted into an S wave component. Consequently, the PS conversion element 8 outputs light which includes a comparatively great amount of an S wave component as a whole.
It is to be noted that the three condenser lenses 11R, 11G and 11B and the three spatial optical modulation elements 12R, 12G and 12B are disposed at three directional positions adjacent three faces of the square cross prism 13. Further, three polarizing plates 17R, 17G and 17B and three polarizing plates 18R, 18G and 18B are disposed on and in parallel to the incoming side and the outgoing side of the three spatial optical modulation elements 12R, 12G and 12B, respectively. In particular, the three polarizing plates 17R, 17G and 17B are adhered to faces on the incoming side of the three condenser lenses 11R, 11G and 11B while the three polarizing plates 18R, 18G and 18B are adhered to three faces on the incoming side of the cross prism 13.
Light from the discharge lamp 6 is uniformed by the fly eye lens set 7 and is converted into light having an adjusted polarization direction by the PS conversion element 8. Of the light L2 having the adjusted polarization direction, light components in the wavelength region of red are reflected by the dichroic mirror 10R and follow the path P3 until they are irradiated upon the spatial optical modulation elements 12R. Then, light components of the light L2 in the wavelength region of green are reflected by the dichroic mirror 10G and follow the path P4 until they are irradiated upon the spatial optical modulation element 12G. Finally, light components of the light L2 in the wavelength region of blue which have passed through the dichroic mirrors 10R and 10G are reflected by the reflecting mirror 103 and follow the path P5 until they are irradiated upon the spatial optical modulation element 12B.
The liquid crystal projector apparatus 1 is constructed in such a manner as described above, and the three spatial optical modulation elements 12R, 12G and 12G therein modulate the three color lights LR1, LG1 and LB1 with image signals corresponding to the three primary colors of red, green and blue applied thereto. In particular, the polarization planes of lights of predetermined polarization directions which have passed through the polarizing plates 17R, 17G and 17B are rotated by the spatial optical modulation elements 12R, 12G and 12B based on signals applied to the spatial optical modulation elements 12R, 12G and 12B. The predetermined polarization light components whose polarization planes have been rotated in this manner pass through the polarizing plates 18R, 18G and 18B and are introduced as image lights LR2, LG2 and LB2 into the cross prism 13. Then, the three image lights LR2, LG2 and LB2 are synthesized by the cross prism 13, and the synthesized image light L2 of R, G and B is emitted along the optical axis P6 by the projection lens 14 and projected on the screen (not shown) or the like so that a full-color image may be reflected on the screen or the like.
In this instance, the three polarizing plates 17R, 17G and 17B and the three polarizing plates 18R, 18G and 18B disposed in parallel on the incoming side and the outgoing side of the three spatial optical modulation elements 12R, 12G and 12B are incorporated in order to adjust the polarization directions of the three color lights LR1, LG1 and LB1 and the three image lights LR2, LG2 and LB2. Each of the three polarizing plates 17R, 17G and 17B and the three polarizing plates 18R, 18G and 18B is formed from a thin glass plate to which a polarizing film is adhered with a bonding agent. In the polarizing plates 17R, 17G and 17B and 18R, 18G and 18B, a temperature rise is caused by a polarizing action of the same. Therefore, a critical guarantee temperature (normally approximately 70xc2x0 C.) for long term reliability is set for the polarizing plates 17R, 17G and 17B and 18R, 18G and 18B, and if the polarizing plates 17R, 17G and 17B and 18R, 18G and 17B are subject to a temperature higher than 70xc2x0 C., then a seizure or a drop in light transmittance occurs with them. Accordingly, it is necessary to normally cool peripheral portions of the polarizing plates 17R, 17G and 17B and 18R, 18G and 18B.
The PS conversion element 8 is composed of a plurality of glass plates coated with a dielectric film and adhered to each other in a rectangular configuration with a bonding agent, and has a limit to the heat resisting use guarantee temperature of the bonding agent. If the temperature region of the bonding agent exceeds the guarantee temperature, then the transmittance of the light L1 through the bonding agent drops. Consequently, also it is necessary to cool the PS conversion element 8 so that the temperature region may not exceed the guarantee temperature. Further, an extra-high pressure mercury lamp is used most frequently for the discharge lamp 6 and includes a reflector in which a very high voltage lamp valve having an output power higher than 150 W is incorporated. Thus, if the temperature of associated elements around the lamp valve and the inside of the reflector should become higher than the limit temperature, then a devitrification phenomenon (drop of the light transmittance) of the lamp valve occurs. Therefore, also it is necessary to cool the associated elements around the lamp valve adjacent the discharge lamp 6 and the inside of the reflector.
Therefore, in the conventional liquid crystal projector apparatus 1 of the type described above, in order to cool the three polarizing plates 17R, 17G and 17B and the three polarizing plates 18R, 18G and 18B incorporated on the incoming side and the outgoing side of the three spatial optical modulation elements 12R, 12G and 12B, an air blasting fan 21 in the form of a thin axial flow fan is incorporated horizontally in an upwardly directed state at a lower portion of the optical unit case 4 in the outer housing 2 at a position just below the cross prism 13 such that cooling air blasted vertically upwardly from the air blasting fan 21 is blasted vertically upwardly into the optical unit case 4 through three cooling air forwarding ports 22R, 22G and 22B formed in a lower portion 4a of the optical unit case 4 at positions below the three spatial optical modulation elements 12R, 12G and 12B, respectively. Further, the cooling air is exhausted to the outside of the optical unit case 4 through three cooling air exhaust ports 23R, 23G and 23B formed in an upper portion 4b of the optical unit case 4 at positions above the three spatial optical modulation elements 12R, 12G and 12B so that the three polarizing plates 17R, 17G and 17B and the three polarizing plates 18R, 18G and 18B are air-cooled forcibly. Also at a position of the lower portion 4a of the optical unit case 4 just below the PS conversion element 8, an air blasting fan 24 of a small size is disposed such that the PS conversion element 8 is air-cooled forcibly by cooling air blasted vertically upwardly by the air blasting fan 24 similarly. A ventilating fan 25 is disposed in the proximity of the discharge lamp 6 on the inner back face of the outer housing 2 outside the optical unit case 4 such that, when the ventilating fan 25 operates, the discharge lamp 6 and associated elements therearound are air-cooled forcibly by a ventilation system wherein cooling air is sucked into the optical unit case 4 through a cooling air inlet port opened in the lower portion of the optical unit case 4 and then discharged to the outside of the optical unit case 4 through the inside of the reflector of the discharge lamp 6 and the associated elements around the lamp valve until it is discharged to the outside of the outer housing 2.
However, the structure wherein the three polarizing plates 17R, 17G, 17B and the three polarizing plates 18R, 18G and 18B, the PS conversion element 8 and the discharge lamp 6 are forcibly air-cooled independently of each other by the three air blasting fans 21, 24 and 25 which are independent of each other, respectively, is great in number of fans used and hence requires a high cost. Further, the structure makes the entire liquid crystal projector apparatus 1 great in size and heavy in weight and besides provides high noise when the three air blasting fans 21, 24 and 25 operate simultaneously. Further, although the conventional discharge lamp 6 has a protective glass plate applied to the front face thereof, since it is accommodated in the optical unit case 4, if the lamp valve should break, then glass fragments of the lamp valve and so forth are scattered over a wide range in the optical unit case 4 and are liable to have a bad influence on the optical elements 7 to 18 of the optical unit 5. Furthermore, since the cooling air intake port necessary for forced air cooling of the ventilation system by the ventilating fan 25 remains open in the lower portion of the optical unit case 4 at the position below the optical unit case 4, when the lamp valve breaks and is to be exchanged, there is the possibility that glass fragments and so forth of it may possibly be scattered also into the inside of the outer housing 2 of the liquid crystal projector apparatus 1 through the cooling air intake port in the lower portion of the optical unit case 4.
It is an object of the present invention to provide a display apparatus of the projection type wherein, when a lamp valve breaks or is to be replaced, glass fragments and so forth of the lamp valve are prevented from being scattered into the inside of an outer housing of a projector apparatus through a cooling air intake port in a portion of the outer casing below the lamp valve.
It is another object of the present invention to provide a display apparatus of the projection type which uses a comparatively small number of cooling fans to form the overall display apparatus in a comparatively small size and with a comparatively light weight and can forcibly cool optical modulation elements, a light source element and so forth in a high efficiency.
In order to attain the objects described above, according to the present invention, there is provided a display apparatus of the projection type, comprising an optical unit including a light source and optical modulation means for modulating light outputted from the light source with an image signal inputted thereto, cooling means including an air blasting fan for blasting cooling air blasted from the air blasting fan at least to the light source to cool the light source, an outer housing in which the optical unit and the cooling means are incorporated, and a lamp box removably mounted in the outer housing and having the light source accommodated therein, the lamp box including a transparent protective member disposed adjacent a light output port of the light source, the lamp box having a cooling air intake port for taking in cooling air from the cooling means to the light source, the lamp box further including automatic opening/closing means provided adjacent the cooling air intake port for automatically opening the cooling air intake port when the lamp box is mounted into the outer housing but automatically closing the cooling air intake port when the lamp box is removed to the outside of the outer housing.
The automatic opening/closing means provided adjacent the cooling air intake port automatically closes the cooling air intake port when the lamp box is removed to the outside of the outer housing. Consequently, when a lamp valve breaks and is to be replaced, fragments of glass of the lamp valve and so forth are prevented from being scattered into the inside of the outer housing of the projector apparatus through the cooling air intake port in the lower portion of the lamp box.
The display apparatus of the projection type may be constructed such that the cooling air intake port is provided at a lower portion of the lamp box, and the automatic opening/closing means provided adjacent the cooling air intake port is provided at a position spaced by a greater distance from the light source than the protective member in a direction of an optical axis of the light source.
When the lamp valve breaks, fragments of it are stopped by the protective member and drop to the lower portion of the lamp box. However, since the automatic opening/closing means provided adjacent the cooling air intake port is provided at a position spaced by a greater distance from the light source than the protective member in the direction of the optical axis of the light source, the scattering of the fragments can be confined to a range to the protective member disposed adjacent the light output port of the light source. Accordingly, the lamp box can be replaced with the fragments accommodated with certainty therein.
The display apparatus of the projection type may be constructed otherwise such that the cooling means includes an air blasting duct for blasting cooling air blasted from the air blasting fan at least to the light source to cool the light source, and the cooling air intake port of the lamp box is removably associated with the air blasting duct with the automatic opening/closing means interposed therebetween.
Even if, when the lamp valve breaks, a fragment of it should be scattered to the outside through the automatic opening/closing means, since the cooling air intake port is removably associated with the air blasting duct with the automatic opening/closing means interposed therebetween, the fragment remains within the air blasting duct and does not have a bad influence on the optical elements of the optical unit.
Preferably, the air blasting duct further blasts cooling air to the optical modulation means. Thus, since cooling air blasted from the single air blasting fan is blasted to at least two locations of the optical modulation means and the light source by the air blasting duct, the at least two locations of the optical modulation means and the light source can be forcibly air-cooled simultaneously in a high efficiency by the single air blasting fan.
The display apparatus of the projection type may be constructed such that the optical unit includes light decomposition means for decomposing light outputted from the light source into color lights of different wavelength bands, a plurality of optical modulation elements which serve as the optical modulation means and upon which the color lights decomposed by the light decomposition means are irradiated, and light synthesis means for synthesizing the color lights modulated by the optical modulation means into image light, and the air blasting duct includes air amount control means for controlling an amount of air to be blasted to the plurality of optical modulation elements. With the display apparatus of the projection type, the amount of air to be blasted to cool the plurality of optical modulation elements suitably can be controlled.
Preferably, the optical unit includes polarizing conversion means for converting light outputted from the light source into light of a predetermined polarization direction, and the air blasting duct further blasts cooling air to the polarizing conversion means. With the display apparatus of the projection type, the at least two locations of the light source and the polarizing conversion means can be forcibly air-cooled simultaneously with a high efficiency.
Preferably, the display apparatus of the projection type is formed from an air blasting duct for blasting the cooled air sent from the air blasting fan at least to the light source and cooling it and a sirocco fan is used for the air blasting fan. Since a sirocco fan which has a high static pressure is used, the plurality of cooling objects which are positioned in a spaced relationship from each other with the air blasting duct interposed therebetween can be cooled efficiently. Further, since the cooling air intake port of the lamp box is removably associated with the air blasting duct with the automatic opening/closing means interposed therebetween, when the lamp valve breaks, the scattering of fractions of the lamp valve is confined at least to the inside of the air blasting duct, and when the lamp box is to be replaced, it can be removed safely with almost all of the fragments left in the lamp box.